Flood Basalts

A flood basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Flood basalt provinces are often called traps, which derives from the characteristic stairstep geomorphology of many associated landscapes. Eleven distinct flood basalt episodes occurred in the past 250 million years, resulting in large volcanic provinces, creating plateaus and mountain ranges on Earth.[1] The Columbia River Plateau of western North America is the nearest to Colorado and occupiesWashington, Oregon, Idaho, Nevada, and California.

During the middle to late Miocene epoch, the Columbia River flood basalts engulfed about 163,700 km2 (63,200 sq mi) of the Pacific Northwest, forming a large igneous province with an estimated volume of 174,300 km3 (41,800 cu mi). Eruptions were most vigorous from 17–14 million years ago, when over 99 percent of the basalt was released. Less extensive eruptions continued from 14–6 million years ago.[2]


  1. Rampino,Michael R. and Stothers, Richard B. (1988). “Flood Basalt Volcanism During the Past 250 Million Years”. Science 241 (4866): 663–668. doi:10.1126/science.241.4866.663. PMID 17839077
  2. Carson, Robert J. and Pogue, Kevin R. (1996). Flood Basalts and Glacier Floods: Roadside Geology of Parts of Walla Walla, Franklin, and Columbia Counties, Washington, Washington State Department of Natural Resources (Washington Division of Geology and Earth Resources Information Circular 90),p.2.